Answer:
When you're through with that compass
Explanation:
An adverb clause is a dependent clause, that is to say, a group of words that have at least a subject and a verb, but that can not stand on its own. The function of this clause is to modify adjectives, verbs or other adverbs. So, This type of clauses often answers questions such as "Why?", "How?", "When?", "Where?" or "In what circumstances?".
When you're through with that compass is an adverb clause because it has a subject: You, a verb: are, it can not stand on its own as it does not express a complete thought, and it acts as an adverb, that is to say, it modifies the verb "use". Furthermore, it also answers to the When question: When may I use it? Answer: When you're through with that compass.
